1. Field of the Invention
The present invention relates to an image scanner, and more specifically, it relates to a structure for properly positioning an image scanning device.
2. Description of the Related Art
Image scanners that have a scanner body and a document feeder for feeding documents to the scanner body are known. In some of them, the document feeder can open and close like a lid of the scanner body.
When an image of a document placed on a document bed glass is scanned, an image scanning device provided in the scanner body moves in the sub-scanning direction and scans the image of the document. To scan an image of a document placed on a document bed glass will hereinafter be referred to as “flatbed scanning.” When an image of a document being moved on the document bed glass by the document feeder is scanned, the image scanning device moves to a predetermined scanning position and then scans the image of the document in the scanning position. To scan an image of a document being moved on the document bed glass by the document feeder will hereinafter be referred to as “sheet-feed scanning.”
When the document feeder is attached to the scanner body, the position of the document feeder is adjusted in order to ensure a predetermined relation between the scanning position, the position of the document feeder, and the direction in which a document is moved.
Japanese Patent Laid-Open No. 10-224553 discusses an image scanner in which an image scanning device of a scanner body is pressed against a document-conveying roller of a document feeder in order to ensure the position of the image scanning device relative to a document.
Japanese Patent Laid-Open No. 10-142851 (corresponding to U.S. Pat. No. 6,027,109) discusses an image scanner including a document feeder that has a sheet feeding device, a sheet conveying device, and a sheet discharging device formed as a unit, the unit having a projection to be pressed against the upper surface of a platen glass of a scanner body. The unit is positioned relative to the scanner body in the vertical direction. Therefore, when the document feeder is attached to the scanner body, adjustment in the vertical direction is made easy.
However, in the image scanner of Japanese Patent Laid-Open No. 10-224553, when adjustment of the document feeder is performed, a document is actually moved by the document feeder and it is calculated from the scanned image how much adjustment is required. Therefore, the adjustment takes a lot of time. In addition, when a document is actually moved and scanned, the scanned image varies depending on the condition of the document and the condition of the conveyance, and therefore it is difficult to achieve accurate adjustment.
Moreover, it is difficult to accurately position the image scanning device relative to the document feeder even if the image scanning device is pressed against the document-conveying roller. Therefore, it is difficult to ensure the relation between the scanning position, the position of the document feeder, and the direction in which a document is moved.
In the image scanner of Japanese Patent Laid-Open No. 10-142851, when the document feeder is attached to the scanner body, adjustment in the vertical direction is not needed. However, a document moved by the document feeder can skew relative to the scanner body. Therefore, the document feeder needs to be adjusted relative to the scanner body so that the document does not skew.